If I play Stand United and buff one unbuffed unit while two other units are already buffed, do the already-buffed units get +1 or +2?

Ruling: All units will receive +2 Might total. The effect that gives buffs an additional +1 Might is separate from the act of adding a buff to a unit.

Nuances:

• The "buffs give an additional +1 Might" effect applies to all buffed units in the battlefield, not just the unit receiving the new buff
• Previously buffed units benefit from the additional +1 Might modifier even though they don't receive a new buff token